※ 引述《lukk790326 (mmmm)》之銘言：
: 不好意思~~可以提示這題如計算嗎6. 6. The point on the curve y = x2 that is closest to the point (18,0) is .謝謝
_______________
d = √(x-18)^2 + y^2
令M = (x-18)^2 + y^2 = (x-18)^2 + x^4
dM
-- = 4x^3 + 2x - 36 = 2(x-2)(2x^2 + 4x + 9) = 0 => x=2 為臨界點
dx
d^2 M
-----| = 12*4 > 0
dx^2 |x=2
當x=2時有極小值272 ,最短距離為 √272 ,
(x,y) = (2,4)
--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 58.115.131.30
※ 編輯: GLP 來自: 58.115.131.30 (05/07 00:21)